I’d guess PIE = play in editor, but even with my old system I’ve never noticed it take much (if any) time.
Like John said it’ll be great for:
Compiling Shaders, compiling UE4/C++ code, running lightmass and some other external programs like World Machine.
For actually playing/testing your game these won’t offer the best performance.
EDIT:
Some links: http://www.legitreviews.com/amd-ryzen-7-1700-overclocking-best-ryzen-processor_192191